KEEPING FIT: On the pulse of heart rate training

By Wayne R. Westcott, Correspondent

Sunday

Aug 12, 2018 at 2:03 PM

You have probably read or heard about heart rate training. You may even have a heart rate monitor that provides moment by moment feedback on your heart rate as you exercise. You may know that your maximum attainable heart rate is predicted to be approximately your age subtracted from 220, and that endurance exercise should be performed between 60 and 90 percent of this number. For example, if you are 50 years old then your maximum attainable heart rate is predicted to be 170 beats per minute (220-50=170). This number indicates that the highest level of physical activity you can perform will raise your heart rate to 170 beats per minute.

Maximum effort aerobic activity, such as running or cycling, requires maximum oxygen delivery to the working muscles. This is accomplished by breathing harder and faster to get as much air (oxygen) as possible into the lungs. This is accompanied by your heart muscles contracting harder and faster to transport as much oxygen as possible through the cardiovascular system to the active muscles. Harder heart muscle contractions force more oxygen-rich blood into your arteries every time your heart beats. More frequent heart muscle contractions force more oxygen-rich blood into the arteries every minute. For example, an exercise heart rate of 140 beats per minute represents twice as many heart contractions every minute as a normal resting heart of 70 beats per minute.

Although sophisticated equipment is necessary to measure the force of your heart muscle pumping actions, it is relatively easy to count the number of times your heart beats per minute. There is a direct relationship between your heart rate and the intensity of your exercise session, and there is an inverse relationship between your heart rate and the duration of your exercise session. For example, if you run at a relatively fast 8-minute mile pace for 15 minutes, your heart rate may average 85 percent of maximum. If you run at a relatively moderate 9-minute mile pace for 30 minutes, your heart rate may average 75 percent of maximum. If you run at a relatively slow 10-minute mile pace for 45 minutes, your heart rate may average 65 percent of maximum. Each of these running sessions should provide a productive cardiorespiratory conditioning stimulus, with exercise heart rate between 60 and 90 percent of maximum heart rate. Assuming a maximum heart rate of 170 beats per minute, an 85 percent exercise intensity would correspond to about 145 heart beats per minute; a 75 percent exercise intensity would correspond to about 128 heart beats per minute; a 65 percent exercise intensity would correspond to about 110 heart beats per minute.

Although this is a simple and practical means for assessing and monitoring your training intensity, the accuracy of this procedure is dependent upon your estimated maximum heart rate. Given the formula of 220 minus age, a 40-year old man or woman is assumed to have a maximum attainable heart rate of 180 beats per minute. However, due to the considerable variation in individual heart rate maximums, a perfectly healthy person at age 40 could have a maximum heart rate between 150 and 210 beats per minute (180 plus or minus 30).

It is therefore important to compare your training heart rate with your subjective perception of exercise exertion. For example, exercising at 75 percent of your maximum heart rate should require moderate exertion. If your actual maximum heart rate is 180 beats per minute, then exercising at 135 beats per minute (75 percent of 180) would be a moderate effort. However, if your actual maximum heart rate is 210 beats per minute, then exercising at 135 beats per minute (65 percent of 210) would be a relatively low effort. Conversely, if your actual maximum heart rate is 150 beats per minute, then exercising at 135 beats per minute (90 percent of 150) would be a relatively hard effort.

Do your best to determine the approximate heart rate that corresponds to a moderate exercise effort and consider this to be about 75 percent of maximum heart rate. If it is somewhat higher than the value predicted by the formula, you most likely have a higher maximum heart rate. If it is somewhat lower than the value predicted by the formula, you most likely have a lower maximum heart rate.

As you train, try to correlate your perceived level of exertion with your exercise heart rate. If your effort level is high, reduce your training intensity to a moderate level and note this heart rate response. If your effort level is low, increase your training intensity to a moderate level and note this heart rate response. Once you have identified the appropriate target heart rate, you can use this information for progressing and adjusting your training program. For example, as you improve your aerobic fitness your heart rate will be lower during your standard exercise session. This is a clear indication that you may increase your training intensity to experience further cardiorespiratory benefits.

While the combined feedback of exercise exertion and training heart rate provides important information for performance enhancement and fitness development, be sure to check with your personal physician before beginning your conditioning program. This is even more essential if you have any cardiovascular issues or are taking associated medications that may alter your heart rate response to exercise.

Wayne L. Westcott, Ph.D., teaches exercise science at Quincy College and consults for the South Shore YMCA. He has written 28 books on physical fitness and strength training.